The Accounting Entry for Buying and Selling Currency — How to Record a Trade Correctly

Every FX trade, however simple it may seem, is a complete financial event: something enters your till and something leaves it. If this movement is not recorded correctly, the balances add up but do not reflect reality. The problem is that many exchange operators see a trade as "one number" — "I sold 1000 dollars" — whereas in accounting every trade has two sides that must be recorded simultaneously and equally.

This article shows exactly that: when you buy or sell currency, what is debited and what is credited, and why this simultaneous double-entry recording both keeps the balance correct and makes your position and profit clear. To see where this discussion fits in the bigger picture, the complete guide to currency exchange accounting and operations is a good starting point.

Why every trade has two sides

The fundamental rule of double-entry accounting is simple: nothing comes from nowhere and nothing goes to nowhere. If dollars entered your till, something equal to it has certainly left — rials, euros, or a liability you have created. The sum of debits must always equal the sum of credits; this balance is the guarantor of the ledger's health.

At an exchange this rule has one added complication: the ledger must balance separately in each currency. That is, when dollars move, the rial side of the trade is recorded in the rial account and the dollar side in the dollar account — rather than everything being converted to one unit and mixed. If you want to understand more deeply why an exchange's general ledger is different, the currency exchange general ledger opens up this topic.

Example 1: recording a currency purchase

Suppose a customer comes and sells you 1000 dollars (that is, you are buying). Your buy rate is 90,000 tomans. So you pay 90,000,000 tomans for this trade.

In this trade two things happen at once: dollars enter your till and rials leave the till. Its double-entry record is this:

The debit side means your dollar asset has increased; the credit side means your rial asset has decreased. Note that these two are in two different currencies and each balances in its own account. Here the rate of 90,000 is simply the "price" of this trade; the rate itself records nothing, but is the bridge that determines the rial amount of the second side.

Example 2: recording a currency sale

Now the reverse. Another customer comes and wants to buy 1000 dollars from you. Your sell rate is 91,500 tomans, so you take 91,500,000 tomans from them.

Here too, two things happen at once: dollars leave your till and rials enter your till. The entry looks like this:

Note that the debit and credit sides are swapped relative to the purchase example. Now rials have been added to your assets (debit) and dollars have decreased (credit). It is this simple symmetry that guarantees your dollar till and rial till always reflect reality.

Where is the profit? Look at the spread

If you place these two trades side by side, an important point emerges. You bought 1000 dollars at 90,000 tomans and sold that same 1000 dollars at 91,500 tomans. The difference between these two rates — 1,500 tomans per dollar — is your spread or profit margin. On 1000 dollars, it comes to 1,500,000 tomans.

The key point is that this profit does not come directly out of the buy or sell entry itself; neither of the two entries above has a "profit" line. Profit is the result of the rate difference between two trades and reveals itself when you close your currency position or produce a profit and loss report. This is why separating the buy and sell rates matters; if you want to understand the logic behind these two rates, buy/sell rate and spread explains exactly this.

The effect of a trade on the currency position

Beyond the balance, every trade also moves your position. After the purchase in example 1, your dollar position became 1000 dollars positive (long). After the sale in example 2, it returned to zero. Had you only bought and not sold, you would have remained open 1000 dollars and exposed to rate movement.

This means the accounting entry is not merely an "archive of the past"; it is your real-time risk management tool. An exchange that records its trades correctly knows at every moment how open it is in each currency and how exposed it is to rate change. An exchange that does not do this is effectively trading in the dark.

Why manual recording is dangerous

So far everything looks clean on paper, but in practice, writing these entries by hand is a source of error. Debit and credit get swapped, one side of the trade is forgotten, the rial amount is miscalculated, or the trade is recorded in the wrong currency. Each of these creates a balance that seems correct but is inwardly wrong. A full list of these errors and how to prevent them is in 7 trade entry mistakes.

The correct solution is that the double-entry record should not be separate from the recording of the trade itself. In Nexto, when you enter a trade — you say which currency, what amount, at what rate, buy or sell — the system builds the multi-currency double-entry record itself: the currency side in that currency's account, the rial side in the rial account, and its effect on position and profit is calculated immediately. You record a trade, not an accounting entry; the entry is its automatic result.

Conclusion

Every currency buy and sell has two sides that must be recorded simultaneously, equally and in the correct currency. In a purchase, the currency is debited and the rial credited; in a sale, the reverse. Profit does not come directly out of either of these entries, but arises from the difference between the buy and sell rates (the spread) and is seen in the position and the profit and loss report. When this double-entry record is built automatically from within the trade itself, human error is eliminated and at every moment you know where you stand in the market.